From TFA, emphasis added: "The company purchases the data from brokers who cull public records, store loyalty program transactions, and credit card purchases."

Store loyalty programs do track SKU-level purchases. There was a case years ago where a patron tripped and fell at a store, and filed a personal injury suit. The store pulled up that person's loyalty program records, noted that they'd been purchasing a larger than average amount of alcoholic beverages, and insinuated at trial that the patron might have been drunk.

Guess who won that case.